Ch.37 Transport in Plants

Long-distance water transport is mainly driven by the ________ of water from leaf surfaces.

evaporation

What is the major stress imposed by flooding?

The loss of available oxygen in the soil

If a cell has a solute potential of -0.5 MPa and a pressure potential of 0.2 MPa, then it will be in equilibrium with a solution that has a water potential of which of the following?

-0.3 MPa

Order the steps that lead to early morning guttation, beginning with the first step.

1) Root xylem accumulates high concentrations of ions. 2) Water follows the ions into the interior of the root. 3) Water is pushed upward in the xylem. 4) Droplets of water are observed on leaves.

Select all plant responses to flooding.

Abnormal growth Hormone levels charge

What plant hormone mediates stomatal closure during daytime water stress?

Abscisic acid

Cavitation in the xylem water column results from which of the following?

Air bubbles

The movement of water across membranes is aided by transport channels called which of the following?

Aquaporins

What types of plants typically form aerenchyma?

Aquatic plants

Select all environmental conditions in which water stress in common.

Arid environments Freezing temperatures Windy environments

Select all true statements about transpiration.

It is driven by evaporation It creates tension in the xylem

How are simplastically transported minerals able to bypass the endodermal barrier that limits apoplastic transport?

By moving through the endodermal cytosol

What gas enters plants through the stomata and is used for photosynthesis?

CO2

The selective uptake of minerals into roots is possible due to the pressure of

Casparian strips

When a gas-filled bubble blocks a xylem element, dehydration and plant death can occur as a result of when of the following?

Cavitation

What directly drives phloem transport between cells of sugar source and sink?

Differences in turgor pressure

Water always moves in which direction?

From an area of higher water potential to an area of lower water potential

The function of succulent leaves in mangroves is to do which of the following?

Dilute salt

Select all physical forces that influence long-distances water transport in the xylem.

Evaporation of water at plant surfaces Cohesion of water molecules to each other Tension that pulls water through the cells Adhesion of water to the walls of conducting cells

Select all factors that lower the water potential of the soil.

Excess fertilizer Drought conditions

True or false: In the phloem, organic molecules are only transported from the roots to the shoots.

False Transport occurs both up and down the plant through the phloem.

Name the kidney-shaped structures that border stomata.

Guard cells

Select all plant adaptations to drought, including those that limit water loss.

Hard, thick leaves Dormancy Loss of leaves

Under what conditions would you expect to see the highest transpiration rates?

High temperature and low humidity

If the water potential outside a cell is -0.3 MPa and the water potential inside the cell is -0.5 MPa, water will move how?

Into the cell

Select all true statements about osmosis.

It carries molecules along a concentration gradient It requires a membrane

Select all statements that accurately describe functions of evaporation for plants.

It helps to cool above-ground portions of the plant It helps to distribute water throughout the plant body It aids in the movement of dissolved minerals for long distances

Select all true statements about transpiration.

It is the primary way in which water is transported long distances in plants. It moves water upward from roots to leaves.

Sucrose is an important compound in plants for which reason?

It is the transport form of carbohydrates.

Select all true statements about blue light.

It promotes K+ transport against a concentration gradient It triggers proton transport, driving the opening of K+ channels

While walking through a field that has been flooded with rain water for several weeks, you notice that plant leaves are dying out. Why would the leaves dry out when water is abundant?

Lack of oxygen in the roots

Select all ways in which plants have evolved to prevent excessive water loss by transpiration.

Leaf drop Regulation of stomata opening

In response to drought, abscisic acid allows potassium ions to do which of the following?

Leave guard cells, causing them to close

Select all functions of stomata.

Minimize water loss Admit carbon dioxide

What happens when solute concentrations increase inside guard cells?

Osmotic water uptake occurs via plasma membrane aquaporins

Match each type of diffusion with description.

Passive diffusion -- The transport of molecules across a membrane without the aid of transport proteins. Facilitated diffusion -- The transport of molecules across a membrane with the aid of transport proteins.

Difference in turgor pressure drive the transport of carbohydrates through structure?

Phloem

This vascular tissue transports organic molecules, such as sucrose, in both directions (from roots to leaves and from leaves to roots).

Phloem

The pressure-flow hypothesis describes which of the following?

Phloem transport

Select all places where aquaporins are found.

Plasma membrane Vacuolar membrane

Select all information needed to predict water movement using the water potential equation.

Pressure at the cell wall-membrane interface Solute concentration inside the plant cell Solute concentration outside the plant call

In early spring, as the buds of a tree are just beginning to open, the main source and sink are which of the following?

Roots and buds, respectively

The carbohydrate-rich fluid that moves throughout the plant is which of the following?

Sap

Select all ways in which plants can manage salt balance in a high salinity environment.

Secretion Exclusion Dilution

Name the structure that allows a plant to take up carbon dioxide for photosynthesis.

Stoma

Plant sap is rich in which of the following?

Sucrose

Which environmental factor affects the turgor pressure of guard cells?

Sunlight

The function of pneumatophores in mangroves is to do which of the following?

Take up oxygen

Why do many plants have vessels, when tracheids are narrower and consequently have higher tensile strength?

The benefits of high mass flow are important in vessels

The plasma membranes of cells in the endodermis contain many different proton pumps involved in the transport of minerals. What do these proton pumps do?

They transport specific ions into the stele against their concentration gradient.

How are minerals typically transported across the endodermis, in order to increase their concentration in the stele?

Through active transport

Select all cell types that carry minerals through a plant.

Tracheids Vessel elements

This type of evaporation drives water movement through the xylem.

Transpiration

What provides the main force for moving water from roots to leaves in the xylem?

Transpiration

True or False: Root pressure is present even when the transpiration rate is low.

True

What vascular tissue carries water molecules and dissolved minerals?

Xylem

The plant hormone that regulates stomatal opening in response to drought is _______ acid.

abscisic

Minerals move through the endodermis to the stele via

active transport

Aquatic plants produce specialized parenchyma with large air spaces, called ______ to allow oxidative respiration to occur.

aerenchyma

Transpiration rate increases with

an increase in guard cell turgor pressure

In contrast to the symplast, the _______ is composed of cell walls and intercellular spaces.

apoplast

A substance that moves through the space between cells is following the _________ route.

apoplastic

The bulk flow of water across membranes is permitted by water channels called ________.

aquaporins

Turgor pressure requires

cell walls to constrain the expansion of cells as they take up water

If you measure atmospheric humidity and transpiration rate in a tree, you will find that as humidity increases, transpiration rate

decreases

In roots, water and nutrient flow are controlled by Casparian strips embedded in cells of the _______.

endodermis

The cells that border stomata are called _______ cells.

guard

Plants that can tolerate saline soils are called _____.

halophytes

The high tensile strength of water results from the cohesiveness of water molecules for each other and adhesiveness to the wall of cells in the xylem. These are both due to the effects of

hydrogen bonding

Guard cells open when their solute concentrations

increase

Select all functions of the edt1 gene in Arabidopsis

increase root length enhance ABA levels

A long-term effect of flooding may be

leaf death due to root damage

Saline soil causes water stress in plants because it has a ______ water potential.

low

When guard cells are turgid, the stomatal pore opens between them, allowing air exchange with the spongy _______.

mesophyll

Flooding damages plants because _______ deprivation leads to decreased cellular respiration.

oxygen

Carbohydrates enter sieve tubes during the process of ______ loading?

phloem

Carbohydrates in storage organs are converted into sucrose and transported through the

phloem

Carbohydrates manufactured in leaves are distributed throughout the plant through the

phloem

The accumulation of sucrose in sieve tube members occurs as a result of

phloem loading

If a cell loses water, the cell membrane pulls away from the wall in a process called ______.

plasmolysis

In the water potential formula, turgor pressure is referred to as _______ potential.

pressure

The accumulation of ions in roots results in the creation of root ______.

pressure

The model for phloem transport is called the _________-_________ hypothesis.

pressure-flow

An important function of pits in vessel walls is to

prevent air bubbles from passing to adjacent vessels

The high tensile strength of water is important for

pulling water up the transpiration stream

Mechanisms to manage _____ stress include exclusion, dilution, and concentration.

salt

Carbohydrates in the phloem move from source to ______.

sink

The total water potential of a cell is obtained by adding the pressure potential and _____ potential.

solute

Carbon dioxide enters leaves through openings between guard cells, called ______.

stomata

Crassulacean acid metabolism (CAM) plants conserve water in dry environments by opening _____ at night.

stomata

Structural features on leaf epidermal cells, called ______, have evolved to minimize water loss, while allowing carbon dioxide uptake.

stomata

Under mild drought conditions, plants may be stunted because

stomata are closed so carbon dioxide is not taken in for photosynthesis

A substance moving from cell to cell through plasmodesmata is following the

symplast route

Select all forms of tissue-level transport.

symplastic apoplastic transmembrane

Unlike C3 plants, CAM plants

take up CO2 at night

The ______ strength of a column of water varies inversely with the diameter of the column.

tensile

The current explanation for the movement of water through the xylem is called the cohesion-_______ theory.

tension

If radioactive carbon dioxide is applied to a plant in a sunny dry atmosphere and another plant in a sunny humid atmosphere, and photographic film is placed over the plants,

the plant in the humid atmosphere will produce a darker image because it contains more radioactive carbon

Select all ways in which plants may encounter water stress in natural environments.

too little water too much salt too much water

Tissue-level transport occurs in three forms: ________, _______, and _______ transport.

transmembrane symplastic apoplastic

The movement of sugars from the cytoplasm into a vacuole is an example of

transmembrane transport

Evaporation of water from leaves, referred to as _______, benefits plants because it cools their surfaces and enables the movement of water from the soil to leaves.

transpiration

The main force for moving water from roots to leaves is called ______.

transpiration

A cell that is swollen with water is said to be _______.

turgid

Stomata open when the _______ pressure in guard cells increases.

turgor

The hydrostatic pressure that builds as water enters plant cells is a form of osmotic pressure called ______ pressure.

turgor

Plant strategies to limit _____ loss include dense trichomes, thick leaves, and placing stomata in pits.

water

Plants are always dealing with the trade-off between open stomata, in which CO2 is taken in but ______ is lost, and closed stomata, in which the same compound is retained, but CO2 is not taken in.

water

The Greek letter psi is an abbreviation for _____ potential, which predicts the direction of water movement in a plant.

water

The _____ potential of saline soils is low, so it causes water stress in plants.

water

When stomata are open and the atmospheric humidity is low, _____ vapor exits the plant.

water

Evaporation aids in the movement of ____ and dissolved _____ over long distances in plants.

water minerals

What type of gradient enables transport from roots to shoots in the xylem?

water potential

Evaporation of water in a leaf creates negative pressure in the xylem. This causes

water to be pulled up the stem from the roots

Water and dissolved minerals are carried through the vascular tissue called ______.

xylem

Water solutions that pass through the membranes of root endodermal cells will enter which structure?

xylem

The solute potential of pure water is _____.

zero